Quantum theory for the dynamic structure factor in correlated two-component systems in nonequilibrium: Application to x-ray scattering

Vorberger, Jan; Chapman, D. A.

doi:10.1103/physreve.97.013203

Cited by 7 publications

(4 citation statements)

References 101 publications

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“…Theoretical methods for WDM out of equilibrium are even more challenging than equilibrium applications that were discussed above. They include time-dependent DFT [69,219], semiclassical kinetics [78], quantum kinetic theory and nonequilibrium Green functions [44,83,220,221], hydrodynamics [80,88,222] or rate equations [223]. Among the problems that were studied are the equilibration of the electron distribution by electron-electron collisions [83,220], non-thermal melting induced by fs xray pulses [219], the density response for nonequilibrium momentum distributions [79,221], density evolution following short-pulse laser excitation [78], collisional heating of quantum plasmas by a laser pulse [224,225], or ionization dynamics in a short laser pulse [80].…”

Section: Wdm Out Of Equilibriummentioning

confidence: 99%

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Ab initio simulation of warm dense matter

et al. 2020

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Warm dense matter (WDM) -an exotic state of highly compressed matter -has attracted high interest in recent years in astrophysics and for dense laboratory systems. At the same time, this state is extremely difficult to treat theoretically. This is due to the simultaneous appearance of quantum degeneracy, Coulomb correlations and thermal effects, as well as the overlap of plasma and condensed phases. Recent breakthroughs are due to the successful application of density functional theory (DFT) methods which, however, often lack the necessary accuracy and predictive capability for WDM applications. The situation has changed with the availability of the first ab initio data for the exchange-correlation free energy of the warm dense uniform electron gas (UEG) that were obtained by quantum Monte Carlo (QMC) simulations, for recent reviews, see Dornheim et al., Phys. Plasmas 24, 056303 (2017) and Phys. Rep. 744, 1-86 (2018). In the present article we review recent further progress in QMC simulations of the warm dense UEG: namely, ab initio results for the static local field correction G(q) and for the dynamic structure factor S(q, ω). These data are of key relevance for the comparison with x-ray scattering experiments at free electron laser facilities and for the improvement of theoretical models.In the second part of this paper we discuss simulations of WDM out of equilibrium. The theoretical approaches include Born-Oppenheimer molecular dynamics, quantum kinetic theory, timedependent DFT and hydrodynamics. Here we analyze strengths and limitations of these methods and argue that progress in WDM simulations will require a suitable combination of all methods. A particular role might be played by quantum hydrodynamics, and we concentrate on problems, recent progress, and possible improvements of this method.

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Section: Wdm Out Of Equilibriummentioning

confidence: 99%

“…by Gericke et al [79]. For these situation, a nonequilbrium quantum kinetic theory is required that yields the time-dependent density response, eq (q, ω; t) [221] and local field corrections, G eq (q, ω; t)…”

Section: H Limitations and Further Improvement Of Qhd: Nonlocal And E...mentioning

confidence: 99%

Ab initio simulation of warm dense matter

et al. 2020

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“…WDM is nowadays routinely realized at large research facilities like NIF [18,19], LCLS [20,21], and the European X-FEL [22]. Here Xray Thomson scattering (XRTS) [23][24][25] has emerged as an important method of diagnostics, with the electronic dynamic structure factor S(q, ω) being the central quantity. However, to make XRTS a reliable tool, an accurate theoretical description of the dynamic density response of warm dense electrons is indispensable [26].…”

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confidence: 99%

Ab initio Path Integral Monte Carlo Results for the Dynamic Structure Factor of Correlated Electrons: From the Electron Liquid to Warm Dense Matter

et al. 2018

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The accurate description of electrons at extreme density and temperature is of paramount importance for, e.g., the understanding of astrophysical objects and inertial confinement fusion. In this context, the dynamic structure factor S(q, ω) constitutes a key quantity as it is directly measured in X-ray Thomson (XRTS) scattering experiments and governs transport properties like the dynamic conductivity. In this work, we present the first ab initio results for S(q, ω) by carrying out extensive path integral Monte Carlo simulations and developing a new method for the required analytic continuation, which is based on the stochastic sampling of the dynamic local field correction G(q, ω). In addition, we find that the so-called static approximation constitutes a promising opportunity to obtain high-quality data for S(q, ω) over substantial parts of the warm dense matter regime.Over the recent years, there has been a remarkable spark of interest in so-called warm dense matter (WDM), an extreme state with high densities (r s = a/a B ∼ 1, a is the mean interparticle distance and a B the Bohr radius) and temperatures (θ = k B T /E F ∼ 1, with E F = 2 q 2 F /2m and q F = (9π/4) 1/3 a B /r s being the Fermi energy and wave number). These conditions occur, for example, in astrophysical objects such as white and brown dwarfs [1-5] and giant planet interiors [6-10], hot-electron chemistry [11,12], laser-excited solids [13], and along the compression path in inertial confinement fusion experiments [14][15][16][17]. WDM is nowadays routinely realized at large research facilities like NIF [18,19], LCLS [20,21], and the European X-FEL [22]. Here Xray Thomson scattering (XRTS) [23-25] has emerged as an important method of diagnostics, with the electronic dynamic structure factor S(q, ω) being the central quantity. However, to make XRTS a reliable tool, an accurate theoretical description of the dynamic density response of warm dense electrons is indispensable [26].In this Letter, we focus on the uniform electron gas (UEG), one of the most fundamental model systems in physics and quantum chemistry [27,28]. While the static properties of the UEG in the ground state have mostly been known for over three decades [29][30][31][32], the intricate interplay of Coulomb coupling and quantum degeneracy effects with thermal excitations has rendered a thermodynamic description in the warm dense regime a challenging problem that has only been solved recently [33][34][35], see Ref.[36] for an extensive review. Naturally, dynamic simulations of electrons that are required for frequencyresolved properties (dynamic conductivity, optical absorption, collective excitations etc.) and rigorously take into account all aforementioned effects are even more difficult. Therefore, results for S(q, ω) at WDM conditions that go beyond the random phase approximation (RPA) [37] are sparse and have been obtained using uncontrolled approximations, such as diagram-summationbased Green function techniques [38][39][40][41]. On the other hand, ab initio path integral Mo...

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“…Over the past decades the Thomson scattering technique has become an indispensable diagnostic tool for ionospheric [7][8][9][10][11] and many types of laboratory plasmas [12][13][14][15][16][17][18]. But the interpretation of the scattering spectra is still a matter of intensive research.…”

Section: Introductionmentioning

confidence: 99%

A signature of non-local plasma fluctuations in Thomson scattering

Puchkov¹

2019

Phys. Scr.

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Thomson scattering from plasma fluctuations in a plasma layer with an electron density maximum is considered. It is shown that the scattering spectrum shape is highly dependent on whether the fluctuations are local or not local. Using the example of Langmuir fluctuations, we demonstrate how non-locality effects manifest themselves by the occurrence of the oscillatory structure in the spectrum. In our case, the non-locality lies in a limited damping and the coupling of fluctuations in different locations where the scattered waves are generated. At the same time, the non-locality may exist even if the damping length for the fluctuations is significantly less than the plasma layer width. The results of the paper show that taking into account the nonlocality may be important for improvement of the fluctuation models and for interpreting the Thomson scattering experiments. Specific calculations presented in the paper allow for finding additional information about plasma parameters from Thomson scattering experiments.

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Quantum theory for the dynamic structure factor in correlated two-component systems in nonequilibrium: Application to x-ray scattering

Cited by 7 publications

References 101 publications

Ab initio simulation of warm dense matter

Ab initio simulation of warm dense matter

Ab initio Path Integral Monte Carlo Results for the Dynamic Structure Factor of Correlated Electrons: From the Electron Liquid to Warm Dense Matter

A signature of non-local plasma fluctuations in Thomson scattering

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